The invention relates to a method of and a device for electrostatic development of charge images on a smooth, tape-like record carrier in a liquid, by guiding the record carrier through a developer tank through which developer liquid continuously flows.
In the electrophotographic copying technique, liquid developer systems are known in which a sheet provided with electrostatic charge images is either immersed in a tank containing the liquid developer, or is supplied to rollers which spread the developer over the sheet. In the former case, either the sheet or the liquid developer must continuously remain in motion, so that the liquid slides up and down the charged side of the sheet.
It is also known (German Auslegeschrift No. 22 31 327) to pump the liquid developer from a reservoir upwards into a developer tank, so that the developer can emerge from a slot provided in the bottom of the tank. Thus, the sheet to be developed is wetted from below by the liquid which is present in the tank. When the bottom of the holder is arranged to be inclined, the developer slowly flows along the surface of the sheet and is subsequently returned to the reservoir.
This known method of development, however, is not suitable for tape-like record carriers which have a smooth surface and which are used in electrostatic printers, for example, as described in German Offenlegungsschrift No. 24 18 632 to which U.S. Pat. No. 4,028,711 corresponds. The charge images are not completely developed when the tape-like record carrier, preferably made of polyester, is simply immersed in or pulled through a developer tank. This is because the shearing forces in the developer are not sufficient to ensure that the interface layer adhering to the tape-like record carrier is sufficiently thin. Thus, only the toner particles present in the interface layer can be deposited on the electrostatically charge surfaces of the record carrier, so that fresh developer required for complete development is blocked by the laminar interface layer.